N Korea nuclear test puts neighbours on notice

BEIJING: North Korea has once again defied the world to conduct its third nuclear test, taking the hermit kingdom a step closer to a credible nuclear weapon that could theoretically strike the United States or Australia.

A statement from the state-run KCNA news agency confirmed the test, hours after a seismic shock registering about 5 was recorded emanating from the northern region of North Korea, where the two previous nuclear tests were conducted in 2006 and 2009.

''It was confirmed that the nuclear test that was carried out at a high level in a safe and perfect manner using a miniaturised and lighter nuclear device with greater explosive force than previously did not pose any negative impact on the surrounding ecological environment,'' the BBC quoted the statement as saying.

The US Geological Survey said the epicentre of the quake was a kilometre underground and the blast took place at 11.57am Korean time (1.57pm AEDT).

A South Korean official explains the seismic waves recording North Korea's detonation of a miniaturized nuclear device on Tuesday. Photo: Lee Ji-eun

South Korea, Japan and the US are searching for fresh points of leverage that might convince North Korea’s sole ally, China, to intervene and obstruct the nuclear weapons program.

Last week the chairman of South Korea’s Joint Chiefs of Staff, General Jung Seung-jo, pledged to pre-emptively strike against North Korea if it showed intent to use a nuclear weapon ''even at the risk of war''.